Television receiver



1?, 3939. R. BARTHELEMY 2,143,933

TELEVISION RECEIVER Filed Jan. 16, 1955 fa e 5ar7 he/e my Patented Jan.17, 1939 PATENT OFFICE TELEVISION RECEIVER Ren Barthelemy,

Fontenay-aux-Roses, France,

assignor to Compagnie pour la Fabrication des Compteurs et MaterieldUsines a Gaz, Montrouge, France Application January 16, 1935, SerialNo. 2,040 In France January 31, 1934 7 Claims.

The present invention relates to television receivers employing cathoderay tubes such as Braun tubes and cathode ray oscillographs.

In such receivers one of the principal defects encountered in the use ofthese cathode ray tubes, rests in the variation of the luminous spot asa function of the modulation; this modulation is, in general, applied toan electrode known as the Wehnelt cylinder and placed near the cathode.There is thus established a notable concentration of the luminous pointat the same time as there results an increase of the luminous intensityunder the efiect of an important modulation which sets up an undesirablestriation at the brilliant parts of the image.

One object of the present invention is to provide a method whichovercomes these defects, that is to say which avoids the narrowing ofthe lines of analysis whilst maintaining at least in the direction ofthe continuous analysis, the increase of fineness due to the narrowingof the point.

This method consists in introducing into the voltage which produces theslow deviation of the cathode beam, which deviation is perpendicular tothe direction of the lines, a component of small amplitude but of highfrequency which causes the luminous spot to oscillate over space betweentwo consecutive lines and perpendicularly to these lines. If thisvibration be sufliciently rapid, the eye will only see, during ahorizontal scanning, a line of constant thickness, this thickness beingdetermined principally by the high frequency elongation but, thebrilliancy of the line is variable as a function of the modulation. Thenarrowing generally observed on the white parts will no longer bepresent. Moreover, the fineness of analysis is increased for thesebrilliant parts since the spot has diminished in diameter and it is notspread out in the horizontal direction, the high frequency oscillationsonly displacing this spot" vertically.

Another object of the present invention is to provide a televisionreceiver employing cathode ray tubes in which there are incorporatedappropriate means to carry out the above defined method.

The invention is described more fully in the following with reference tothe attached drawing, in which:

Figure 1 is a diagram illustrating the method according to the presentinvention.

Figure 2 is a diagrammatic example of a television receiving apparatusemploying cathode ray tubes in which there is provided an example of themeans for carrying out the method.

In a television receiver employing cathode ray tubes, the scanning ofthe screen by the concentrated cathode pencil is obtained by a rapid 5deviation of the pencil in a horizontal direction simultaneously with aslow vertical deviation. This slow deviation as a function of time canbe shown over the period of scanning of an image by the straight line 0I of Figure 1 which is 1 obtained by marking off, as abscissae thevalues of time and as ordinates the values of the slow deviation. Thesubstantially vertical part I N corresponds to the return of theluminous spot from the end of one image to the beginning of the next. Inthese usual conditions of scanning the screen there is set up, under theeffect of an important modulation, a notable concentration of theluminous spot on the screen at the same time as an increase in theluminous intensity of the same, which results, in the reproduced image,in very troublesome striations at the brilliant parts of the image.

In order to overcome this disadvantage, the method according to thepresent invention consists in causing the luminous spot to oscillateadditionally in the space between two consecutive lines andperpendicularly to these lines at a high frequency and of feebleamplitude. To this effect there is superimposed on the voltage causingthe slow deviation of the concentrated cathode pencil, an oscillatingvoltage having a feeble amplitude and a high frequency.

The object of the method according to the present invention can be showngraphically as in Figure 1, in which a very rapid oscillation S, offeeble amplitude, is superimposed on the slow deviation 0 I during thecourse of the sweeping of the image. By reason of the high frequency ofthe oscillation S the eye, during each horizontal scanning, sees only aline of which the constant thickness is determined by the elongation ofthe additional high frequency oscillation but of which the brilliancyvaries as a function of the modulation. In order to carry thissuperimposition into efiect in a receiver using cathode ray tubes, theadditional high frequency oscillation can be applied to the electrodesof the tubes which control the slow deviation, as shown diagrammatically51 in the example of Figure 2. The cathode ray tube comprises a cathodeC, an electrode known as the Wehnelt cylinder W, an anode A and twopairs of perpendicular deflecting plates P1 P2 and P'i Pz. The verticalplates P1 P2 by means of 5 the voltage which is applied to the samecontrol the rapid horizontal deviation along lines. The horizontalplates P'1 P'2 by reason of the voltage which is applied to them controlthe slow vertical deviation. The slow deviation voltage is applied tothe terminals L1 L2. In .accordance with the method according to thepresent invention there is introduced into the circuit of the slowdeviation plates P'1 Pz, through the intermediary of an inductivecoupling M, for example, an oscillating voltage of high frequency and ofsmall amplitude, furnished by an auxiliary generator G. This oscillatingvoltage, the form of which is shown at S in Figure 1, causes'theconcentrated cathode pencil to oscillate and consequently the luminousspot formed on the screen E oscillates perpendicularly to the directionof the lines. By this means a television receiver is obtained in whichthe troublesome striations are no longer present in the brilliant partsof the image and moreover the finenessof analysis is increased for thesebrilliant parts.

'In practice the value of the additional high frequency voltage needonly be of the order of one volt and it is possible to obtain thisvoltage without using an auxiliary generator. For example, wherethe'receiver is of the superheterodyne type which already possesses ahigh frequency oscillator, the additional high frequency voltage can-befurnished by this oscillator (Fig. 3); it is sufiicient to provideaslight coupling between the oscillator and the circuit of the slowdeviation electrodes Pi P'z.

Another method, which proportions the correction tothe amplitude of themodulation is to use, for the additional high frequency voltage, afraction of the modulated high frequency voltage which is available inthe receiver before detection (Fig. 4) This fraction will act on thecircuit of the slow deviation electrodes in. place of the generator G.In this case there is obtained a greater definition in the half-tonesthan in the case where an additional high frequency voltage of constantamplitude is employed.

What I claim is:

1. A television receiver employing a cathode ray tube having two pairsof perpendicularly arranged electrodes, a circuit associated with one ofthe pairs of electrodes to apply to the same a voltage to cause thecathode pencil to deviate rapidly along parallel lines, and anothercircuit associated with the other pair of electrodes in order to applyto the same a voltage to cause the cathode pencil to deviate slowly in adirection perpendicular to the lines, and means for introducing into thecircuit associated with the slew deviation pair of electrodes anadditional high frequency oscillating voltage of small amplitude.

2. In a television receiver employing a cathode ray tube having twopairs of perpendicularly arranged electrodes, a circuit associated withone of the pairs of electrodes to apply to the same a voltage to causethe cathode pencil to deviate rapidly along parallel lines, and anothercircuit associated with the other pair of electrodes in order to applyto the same a voltage to cause the cathode pencil to deviate slowly in adirection oerpendicularto the lines, means for introducing nto thecircuit associated with the slow deviation aair of electrodes anadditional high frequency )scillating voltage which amplitude is varyingwith the modulation of the modulated wave re- :eived.

3. In a television receiver employing a cathode ray tube having twopairs of perpendicularly arranged electrodes, a circuit associated withone of the pairs of electrodes to apply to the same a voltage to causethe cathode pencil to deviate rapidly along parallel lines and anothercircuit associated with the other pair of electrodes in order to applyto the same a voltage to cause the cathode pencil to deviate slowly in adirection perpendicular to the lines, means comprising an auxiliarygenerator to apply, to the circuit associated with the slow deviationpair of electrodes, an additional oscillating voltage of high frequencyand of small amplitude.

4. In a television receiver of the superheterodyne type employing acathode ray tube having two pairs of perpendicularly arrangedelectrodes, a circuit associated with one of the pairs of electrodes toapply to the same a voltage to cause the cathode pencil to deviaterapidly along parallel lines, and another circuit associated with theother pair of electrodes in order to apply to the same a voltage tocause the cathode pencil to deviate slowly in a direction perpendicularto the, lines, coupling means between the local generator of thereceiver and the circuit associated with the slow deviation pair ofelectrodes in order to apply to the said circuit an additional highfrequency voltage of small amplitude.

5. In a television receiver employing a cathode ray tube having twopairs of perpendicularly arranged electrodes, acircuit associated withone of the pairs of electrodes to apply to the same a voltage to causethe cathode pencil to deviate rapidly along parallel lines, and anothercircuit associated with the other pair of electrodes in order to applyto the same a voltage to cause the cathode pencil to deviate slowly in adirection perpendicular to the lines, means for taking a fraction of themodulated high frequency voltage present before detection and for addingthis fraction'of the voltage into the circuit associated with the slowdeviation pair of electrodes to the voltage causing the cathode pencilto deviate slowly.

6. A method for reconstituting images by means of a cathodicoscillograph, which method consists in modulating the intensity of acathode beam, said modulation corresponding to the modulation of themodulated image current making the impact point of said cathode beam onthe screen of the oscillograph describe parallel juxtaposed lines andgiving to said impact point an additional oscillation perpendicular tothe direction of the lines, of feeble amplitude and of high frequencycorresponding to the frequency of the lines.

7. A method for reconstituting images by means of a cathodicoscillograph, said method comprising modulating the intensity of acathode beam, said modulation corresponding to the modulation of themodulated image current, making the impact point of said cathode beam onthe screen of the oscillograph describe parallel juxtaposed lines andgiving to said impact point an additional oscillation perpendicular tothe direction of the lines, of feeble amplitude, and varying with themodulation of the modulated image current and of high frequencycorresponding to the frequency of the lines.

RENE BARTFE LEMY.

